A Study to Assess the Ability of a Novel Endocrine Treatment for Breast Cancer, Irosustat, to Slow Down Cancer Growth (IPET)

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This study is investigating the effects of a new hormone treatment for breast cancer called Irosustat. Seventy percent of breast cancers in post-menopausal wome rely on oestrogen to grow therefore are likely to respond to hormone therapy. Irosustat blocks a different pathway of steroid synthesis to Aromatase, reducing in this way oestrogen levels in the body. As less oestrogen reaches the breast cancer, it grows more slowly or stops growing altogether.

IPET will recruit postmenopausal women with early, hormone sensitive, treatment naive breast cancer will receive 40mg of Irosustat once daily for 2 weeks. The effects of Irosustat on breast cancer will be evaluated by PET scans (Positron Emission Tomography) using a radioactive substance called FLT as a tracer. The scans will be performed in a PET-CT scanner which combines a PET scan and a CT scan (Computer Tomography) into one scan. This type of scan can show how body tissues are working, as well as what they look like. FLT-PET scans will be performed before and following treatment with Irosustat. As cancer cells grow faster than the normal cells around them, they will take up more of the radioactive substance, and so stand out clearly on the scan. If Irosustat is slowing down the cancer growth, the cancer will take up less of the tracer.

Blood samples will be taken at regular intervals to assess what the new drug does to the body and the safety and tolerability of Irosustat will be assessed. The study incorporates translation aspects/endpoints which are based on the collection of tumour biopsies before and after treatment with Irosustat although the later biopsy is not mandatory.

Irosustat 40mg OD for a minimum of 2 weeks until follow up FLT-PET/CT. For those patients consented to a repeat tumour biopsy, treatment will be extended to that day before the procedure.

Drug: Irosustat

Irosustat will be administered once daily in 40mg tablets. Treatment will start the day after the baseline FLT-PET and will be continued for a minimum of 2 weeks until the follow up FLT PET scan. For those patients who have consented to a repeat tumour biopsy, treatment will be extended to the day before the procedure. Study medication should be taken in the morning under fasting conditions with a glass of water, 30 minutes before breakfast.

Changes in FLT uptake as assessed by PET following 2 weeks of treatment with Irosustat [ Time Frame: Patients will have a baseline FLT-PET/CT scan and a follow-up scan after 2 weks of treatment with Irosustat ]

Secondary Outcome Measures
:

To characterize the pharmacodynamic profile of Irosustat by measuring peripheral blood steroid hormone levels [ Time Frame: Blood samples will be drawn from patients on day 1, day 7, day 14 and 28 days post administration of the last dose of Irosustat ]

To evaluate safety and tolerability of Irosustat by collecting toxicities according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE v 4.03: June 14, 2010) [ Time Frame: Patients will be assesed at baseline, day 7, day 14 and at 30 days following the last dose of Irosustat. Patients who have consented to an optional post treatment tumour biopsy will attend an extra study visit. ]

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Amenorrhoea > 12 months at the time of diagnosis and an intact uterus OR,

prior bilateral oophorectomy OR,

FSH levels within the postmenopausal range (as per local practice) in women aged < 55years who have undergone hysterectomy OR,

FSH levels within the postmenopausal range (as per local practice) in women aged < 55 years who have been on Hormone Replacement Therapy (HRT) within the last 12 months and are therefore not amenorrhoeic

Any clinically important abnormalities in rhythm, conduction or morphology of resting ECG e.g. complete left bundle branch block, third degree heart block

Any factors that increase the risk of QTc prolongation or risk of arrhythmic events such as heart failure, hypokalaemia, congenital long QT syndrome, family history of long QT syndrome or unexplained sudden death under 40 years of age or any concomitant medication known to prolong the QT interval